Cathode ray tube counting device



Jan. 20, 1959 CATHODE RAY W. F. SCHREIBER TUBE COUNTING DEVICE CATHDE RAY TUBE CUNTING DEVICE William F. Schreiber, North Hollywood, Calif., assigner to Sylvania Electric Products Inc., a corporation of Massachusetts Application February 28, 1955, Serial No. 490,750

7 Claims. (Cl. 315-10) My invention relates to electronic switching apparatus and more particularly relates to cathode ray tube circuits for use in such apparatus.V

The prior art has knowledge of circuits of this type in which the cathode ray tube is provided with a plurality of anodes, the electron beam produced within the tube being directed sequentially upon each anode individually in accordance with externally supplied electric pulses. Such tubes require complicated and expensive electrode structures; further, it is a tedious, time consuming, and difficult procedure to mount these electrodes in proper manner withinA the tube envelope.

I have invented a cathode ray tube circuit of the character indicated in which these difficulties are obviated.

Accordingly, itis an object of the present invention to provide a new and improved cathode ray tube circuit of the character indicated.

Another object is to provide a new and' improved cathode ray tube circuit of the character indicated which makes use of a conventional cathode ray tube and a novel externally mounted optical mask or wedge.

Still another object is to provide a new and improved cathode ray tube circuit adapted for use in switching apparatus and including, in operative relationship, a conventional cathode ray tube, an externally mounted optical wedge or mask, a photocell and a feedback amplifier.

Yet another object is to provide a new and improved cathode ray tube circuit of the character indicated which incorporates a novel optical mask or wedge and' which obtains a switching action with the use of one or two dimensional scanning.

These and other objects of the invention will either be explained or will become apparent to those skilled in the art when this specification is studied in conjunction with the accompanying drawings wherein:

Fig. l illustrates an embodiment of the basic invention as applied to one dimensional scanning;

Figs. 2a and 2b illustrate alternate types of optical wedges and masks for use in the apparatus of Fig. l;

Fig. 3 is a diagram illustrating graphically the voltagedeflection characteristic of the invention o-f Fig. l;

Fig. 4 illustrates a second embodiment of the basic invention as applied to two dimensional scanning; and

Fig. 5 illustrates an optical wedge or mask for use with the apparatus of Fig. 4.

In accordance with one main feature of the invention, lprovide a conventional cathode ray tube provided'with means for producing an electron beam, a luminescent screen upon which the beam is directed, and a pair of deflector plates for defiecting the beam in one given dimension, for example, horizontally or vertically. An optical mask provided with a plurality of like sections spaced sequentially along the given direction is positioned infront of theluminescent screen. Each section is transparent and the transparency varies from point to point within each section in theA same manner. As the beampasses over each section, thepassage canbe observed visually.Y A photocell is mounted in front yof the mask 2,870,369 Patented Jan. 2o, 195s and responds to the luminescent information appearing in the mask to develop a voltage proportional thereto. As the beam position within any mask sectionis varied along the given direction, the photocell output voltage will be varied accordingly because of the transparency variations within the section. This varying output volt'- age is amplified, if necessary, and then is supplied as a feedback voltage to the deiiection piates. The purpose of this feedback voltage is tostabilize the beamV position within any section; if voltage supply variations or the like result in beam movement within the section, the feedback voltage will act to restore the beam to its stable position within the section. A beam shifting signal, for example,4 in the form of discretely spaced pulses is also supplied to the deflector plates; this signal is sufficiently large to momentarily override the feedback voltage and thus shift the beam from one section to the adjacent section. Means are further provided to return the beam to itsoriginal position after the beamV has been shifted through all other positions successively. in this fashion the beam attainsl different stable positions in accordancewiththe number of incoming pulses, so that my appara-- tuscan be used, for example, as a counter lor scaler.

In. order to increase the number of stable beam positions beyond that available with one dimensional beam travel or scanning, and thus, for example, increase thel capacity of th'ecounter or sealer, it is necessary to use two dimensional beam defiection; this can be accom.- plished through the use of horizontal and vertical deflection plates normally provided within the cathode ray tube.' To this end, another type of optical mask is re.- quired. This mask is" divided into a plurality of like horizontal segments, eachV segment having a plurality of like sections; Each section has a light transmission chai'-, acteristic such that variations of beam position in the horizontal direction within the section produce light variations in one band of wavelengths, while beam varia.- tions in the vertical direction produce light variations in a second frequency range. A first photocell solely responsive to light variations in the one band of wavelengths supplies a first feedback voltage to the horizontal deection plates to maintain horizontal beam stability; a second photocell solely responsive to lightvariations in the other frequency range supplies a second feedback voltage to the vertical deflection plates to maintain verti` calA beam stability. The system otherwise responds in the same manner as before except that means are required not only to return the beam horizontally after a complete horizontal segment of the mask has been scanned but also to move the beam vertically at the same time so that the adjacent horizontal segment can also be scanned.

Referringnow to Fig. l, there is provided aconvcntional: cathode ray tube with an electron gun and beam forcusing structure identified in block form at 101, verticalv deection plates 102e and 102B, and a luminescent screen 103. Secured to the outside of screen is an optical mask 104. A photocell is mounted adjacent screen 103; The output voltage produced'by photocell 105is supplied to the input 106 of amplifier' 107.A rl`he output of amplifier 107`is connected through resistor 108`v` to deflection plate 10241, to the input 110 of trigger circuit' 111 and to output terminal 112. Incoming dis. cretely. spaced 'pulses with the wave form indicated" are supplied` to input terminal 113. This terminal is con-l nected through resistor 114 to plate 102e. The output 115', of trigger circuit 111 is connected to input 116` of amplifier 107.

Fig. 2a` shows one form of optical mask 104 which can be usedwith the apparatus of Fig.` l. It includes a plurality of sections,.inv this example five sec'tions,lide'r 1{ tied as104a, 10%,- 104C, 104d`and104e. Each sci c 3 tion includes an optically transparent portion and a shaded portion which is appreciably more opaque, the opacity increasing toward the top of each portion. The mask is mounted adjacent screen 103 in such a manner that the long dimension of the screen extends along the beam deflection path.

` Fig. 3 is a composite graph showing a sawtooth pattern which indicates the variation in the output voltage of amplifier 107 with electron beam deflection for the five section mask of Fig. 2a. Superimposed upon this pattern is a line which indicatesY the tube deflection characteristic (i. e., beam deflection vs. deflection voltage). The circled intersections of line and sawtooth represent stable positions of the electron beam. (The uncircled intersections are unstable because a slight random displacement in either direction results/zinY positive feedback; thisY 'positive' feedback'foices'thebeam to move away from any unstable position.) The circled positions are stable because any voltage fluctuation at the plate will shift the beam position, an-d as a result of the optical properties of the mask, will change the voltage output of the photocell. The voltage output from the amplifier will change accordingly. This change in amplifier voltage will be applied to the deflection plates in such manner that the beam will be restored to its original stable position.

' As can be seen from Fig. 3, there is a characteristically different amplifier output for each stable beam position. When the beam attains an extreme horizontal position, Athis amplifier voltage attains such a value that the trigger circuit is activated and produces a shift pulse which after amplification is supplied to the deflection plate to return the beam to its initial horizontal position.

In the absence of a shift pulse, the amplifier output voltage appearing at output terminal 112 is proportional Ito the horizontal beam position, and hence the apparatus of Fig. 1 can be used as a counter.

Fig. 2b shows an alternate type of optical mask 117 wherein each section has a wedge shaped opaque portion. This mask can be used in place of the mask of Fig. 2a if the electron beam is focused to produce a fairly large luminescent spot on the screen so that varying portions of the spot are concealed behind the opaque portion.

For combined horizontal and vertical scanning, the apparatus of Fig. l must be modified as shown in Fig. 4, and a different mask, for example as shown in Fig. 5, must be used.

The mask 200 of Fig. 5 comprises a plurality of like small clear transparent areas 201e, 20115, 201e, 201d, 201e, 201f, 201g, 201k, and 201i. Each of these areas represents a stable beam position. It will be seen that there are threehorizontal groups or arrays, each con-- taining three of the above areas. The number of arrays and included areas can be indefinitely extended to cover virtually the entire surface of the associated cathode ray tube screen.

The mask portions 202 horizontally adjacent to each area and identified by one type of characteristic shading are red colored and transparent. The mask portions 203 vertically adjacent to each area and identified by another type of characteristic shading are blue colored and transparent. Each of thesev portions acts as a light filter for any luminescent spot appearing in the tube screen and has a different frequency transmission characteristic.

The mask 200, which in this case contains one hundred areas in a square ten areas in a side, is mounted adjacent the screen 101 of tube cathode ray tube 100 of Fig. 4. This tube is identical with that of Fig. 1 except that it is also provided with vertical deflection plates 301a and 3011i.

The horizontal deflection plates 102a trigger circuit 111, amplifier 106 and photocell 105 are connected in the same manner as before. However interposed between mask 200 and photccell 105 is a red filter 300. As a result, any horizontal ymotions of the beam about any stable position are corrected by a feedback voltage counter. Moreover, by connecting terminal 312 to a sec- Y as before; the red filter prevents the photocell 105 from being rendered responsive to any vertical motions of the beam.

Vertical deflection plate 302:1 is connected to trigger circuit 311, amplifier 306 and photocell 305 in like manner to the horizontal plate connection. Interposed between mask 200 and photocell 305 is a blue filter 301.

As a result, any vertical motions of the beam about any stable position are corrected by a feedback voltage from amplier 306 in the manner previously described; th

blue filter prevents pho-tocell 305 from being rendered responsive to any horizontal motions of the beam.

Trigger circuit 115 as before is activated when the beam reaches an extreme horizontal position, i. e. has scanned an array. yThe amplified shift pulse returns the 'Y beam ,toY the othern extreme position.V Simultaneously trigger circuit 315 is activated to produce a pulse which, after amplification, shifts the beam to a position Where it can scan the adjacent array.

Output terminal 112 yields an output voltage which is proportioned to the horizontal beam position in any array.

Such a voltage can be considered a units output voltage. Output terminal 312 yields an output voltage which is proportioned to the vertical position of the beam. Such a voltage can be considered a tens output voltage.

Thus the apparatus of Fig. 4 can also be used as a ond like counter it is possible to use these counters in cascade andthus indefinitely increase the counting capacity of the system.

The circuit elements shown in block form in Figs. l and 4 are conventional in type and are not shown in schematic detail. The photocells and amplifiers, for example, can be of the type shown in item J, Fig. 236-11, on page 314, of The Electronic Engineering Handbook, published in 1944, by Electronic Development Associates. The trigger circuits, for example, can be of the type shown in Fig. 6.6 on page '324 of Cathode Ray Tubev Displays, published in 1948 by McGraw-Hill.

While I have shown and pointed out and described my invention in one preferred embodiment, it will be apparent to those skilled in the art that many other modifications can be made within the scope and sphere of my invention as defined in the claims which follow.

What is claimed is:

1. In combination, a cathode ray tube provided with electron beam generating means, deflection plates for deflecting said beam along a given path, and a luminescent screen for visually displaying the path of the deflected beam; an optical mask covering a portion of said screen and extending along the beam deflection path, saidlmask being provided with a plurality of like sections which extend along corresponding segments of the beam deflection path, each section having a light transmission characteristic at which one section subarea exhibits substantially no light attenuation while all other subareas exhibit appreciable light attenuation; means coupled to the deflection plates to position said beam successively in a like plurality of discrete positions, each position being within a corresponding segment of the deflection path; a photoelectric cell responsive to the light transmitted through each mask section to produce a control voltage proportioned to the transmitted light; and means to supply said control Voltage to said deflection plates in a direction at which the beam positions are confined to the portions of deflection path segments which correspond to the unattenuated section subareas.

2. The combination as set forth in claim l wherein each -section is divided into two subareas, one area being optically transparent, the other area being optically opaque.

3. In combination, a cathode ray tube provided with an electron beam source, horizontal and vertical deflection plates for respectively dellecting said beam along horizontal and vertical deflection paths, and a luminescent screen responsive to the deflected beam; an optical mask adjacent said screen and provided with a lirst plurality of small equal optically transparent sections arranged in horizontal and vertical arrays, adjacent horizontal sections being separated from each other by mask material having a lirst light frequency transmission range, adjacent vertical sections being separated from each other by mask material having a second light frequency transmission range, said ranges being separated in frequency; means coupled to said deection plates to cause said beam to successively scan areas corresponding each horizontal array, the beam being discretely shifted from one section to the adjacent section within each horizontal array; irst photoelectric means optically associated with the mask and optically sensitive only to the rst frequency range to produce a iirst control voltage only when the beam is horizontally positioned outside of said sections; second photoelectric means optically associated with the mask and optically sensitive only to the second frequency range to produce a second control voltage only when the beam is vertically positloned outside of said sections; and means to apply said rst and second voltages to said horizontal and vertical plates respectively, whereby stable beam positions are confined to areas corresponding to said sections.

4. A counter responsive to an incoming pulse train comprising a cathode ray tube provided with an electron beam generator, horizontal and vertical deflection plates for deecting said beam both horizontally and vertically, and a luminescent screen for visually displaying the path of beam deection; an optical mask containing a first plurality of horizontal arrays, each array containing a second plurality of small clear transparent areas equally spaced and horizontally separated by iirst mask material which is transparent only to light falling within a first frequency range and is otherwise opaque, each area being separated from vertically adjacent areas by second mask material which is transparent only to light falling within a second and different frequency range and is otherwise opaque; means responsive to said pulse train and coupled to the horizontal plates to deflect said beam horizontally in accordance with said pulses to scan a horizontal array; first photoelectric means optically associated with the mask and optically responsive only to the first range to produce a rst control voltage when the beam is horizontally displaced outside of any of such areas; means to supply said rst control voltage to the horizontal plates in a direction opposing said horizontal displacement in the absence of supplied pulses; means responsive to said rst control voltage and coupled to said horizontal plates to return said beam to the initial horizontal scanning position at the instant any horizontal array has been scanned; second photo-electric means optically associated with the mask and optically responsive only to the second range to produce a second control voltage when the beam is vertically displaced outside of any of said areas; means to supply said second control voltage to the vertical plates in a direction opposing said vertical displacement; and means responsive to said second control voltage and coupled to the vertical plates to shift the beam from one horizontal array to an adjacent horizontal array at the instant the one array has been scanned, whereby the first and second control voltages together indicate the pulse count.

5. A counter as set forth in claim 4 wherein each photoelectric means is provided with a light filter formed from material which has the same light transmission characteristic as the associated mask material.

6. A counter as set forth in claim 5 wherein each of the means responsive to a corresponding control Voltage and coupled to corresponding deflection plates includes a trigger circuit.

7. An optical mask provided with a rst plurality of horizontal arrays, each array containing a second plurality of small clear transparent areas equally spaced from each other and horizontally separated by mask material transparent only to light falling within a rst frequency range, vertically adjacent areas being equally spaced from each other and vertically separated by mask material transparent only to light falling within a second and dilerent frequency range.

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